Air-pump.



No. 805,630. PATENTBD NOV. 28, 1905.

- T. N. CASE. AIR PUMP.

APPLICATION FILED MAY13, 1904.

2 SHEETS-SHEET 1.

N0- 805,630. PATENTBD NOV. 28, 1905. T. N. CASE.

AIR PUMP.

APPLIOATION IILED mm 13, 1904.

9m v U T N m 7 V W/V/F! M m m l w ,V m 7//////////////fi//////////// Fa m m m W Q W (7 -hl A .Jm I WM w fin w I 11 w llxl Ja i THEODORE N. CASE, OF MOUNT VERNON, NEW YORK.

AIR-PUMP.

Specification of Letters Patent.

Patented Nov. 28, 1905.

Application filed May 13, 1904. Serial No. 207,751.

To a whom it may concern:

Be it known that I, THEODORE N. CASE, a citizen of the United States, residing at Mount Vernon, in the county of Westchester, State of New York, have invented certain new and useful Improvements in Air-Pumps, of which the following is a full, clear, and exact description.

My invention relates to improvements in air-pumps, and has for its object to provide a pump which shall be simple in construction and particularly efiicient in action whether used as an air-compressor or as a vacuumpump.

Another object of my invention is to secure a valve system which will admit of employment of a higher rotative speed in elasticfluid pumps than that commonly employed, thereby producing a pump which will do more work in a given time than pumps of the same size of the usual type heretofore employed can do.

Hitherto in air-pumps various means have been employed in connection with slide-valves for keeping the passage between the cylinder and discharge-opening closed until the pressure ahead of the piston is substantially equal to the discharge-pressure. Most of these means when efficient have been expensive and complicated; and it is the purpose of my invention to provide means for accomplishing this end which shall not be open to either of these objections. In doing so I make use of a construction which, while it is subject to various modifications and rearrangements, is set forth in the most desirable forms now known to me in the accompanying drawings, in which Figure l is a longitudinal section of a pump, valve-chamber, and valve on the line re re, Fig. 2. Fig. 1 is an enlarged sectional view of a detail. Fig. 2 is a divided cross-section, the left-hand portion being a section on the line A B, Fig. 1; the right-hand, a section on the line O D, Fig. 1. Fig. 2 is an illustrative view showing a detail. Fig. 3 is a diagram showing the relative positions of the centers of the shaft, crank, and eccentric for operating the piston-rod and the main valve. Fig. 4 is a vertical section of the valve-chamber shown in Fig. 2 with a modified valve substituted. Fig. 5 in its left-hand portion shows a section of the valve shown in Fig. at on the line E F and in its right-hand portion a section of the valve shown in Fig. 4 on the line G H. Fig. 6 is a modification of the valve construcated by the piston-rod 3, which receives its motion from a crank 3 on a crank-shaft 3, Fig. 3, in the ordinary way. The inlet and outlet ports 4t 4:, connecting with the cylinder, are controlled by a piston-valve 5, having a hollow bore 5 and actuated by a valverod 5, which receives its reciprocating motion in the usual way from an eccentric centered at 5 and fixed on the crank-shaft. The inlet 6 connects to each end of the valve-chest at 7 7. The outlet 8 connects with the body of the val vechest. The valve upon the rod 5 works within the fixed sleeves 9 9, which form its seats. In these sleeves are ports 12 12, alternating with bridges 13 13,as shown in Figs.2 and 2. These ports 12 12 are made, as shown, so as to present a wearing-surface to all parts of the periphery of the valve-heads, thus preventing unequal wear. Passages 14 14:, connecting with ports i 4, distribute the fluidair, for exampleto the ports 12 12. For convenience in manufacture, the valve upon the rod 5 is divided at the middle of the barrel, as shown at 15. This permits the mounting of all parts upon the rod 5"- and the clamping of them together by nut 16 and jam-nut 17. The valve is provided with main discharge-ports 18 18, controlling the discharge from the cylinder 1. It is also provided with what may be called auxiliary discharge-ports 19 19', alternating with bridges, as developed in Fig. 2, which are controlled by cylindrical auxiliary slide-valves 2O 20, which are held to their seats by the spring 21, surrounding the barrel of the main valve. This spring 21 engages with both auxiliary valves, so that when pressure through the ports 18 18' is less than that in the space8 between the piston-heads both auxiliary valves will remain in seated position, as illustrated in Fig. 1, closing the ports 19 19, their outer ends 22 22 engaging with shoulders formed on the main valve. hen

the pressure through 18 or 18 is sufficiently greater than that in 8, one of the valves 20 20 will move toward the center of the main valve uncovering 19 or 19, as the case may be, making a connection between 18 or 18 and 8. As

soon as the pressure through 18 or 18 is reduced to or below that of 8, the valve 20 or 20 will move back across the port 19 or 19 and close the same. In order that the auxiliary valves may come to rest easily, cushioning-chambers 23 23 (shown with positions slightly altered in enlarged detail in Fig. l) are provided, connecting by one or more small auxiliary ports 24 24 with the d ischarge-chamber 8. As the auxiliary valves come to rest after closing the ports 19 19, the auxiliary port or ports 24 24 are partially closed by their moving partially across the enlarged portion of the main valve, which serves as a plunger in the cushioningchambers 23 23, thus throttling the escape of air from 23 and 23, compelling the auxiliary valve 20 20 to come to rest slowly.

In order to provide an equalizing-passage connecting both ends of the pump-cylinder 1 when the piston 2 is substantially in either of its extreme positions, ports 25 25 are provided connecting with the hollow bore of the main valve and so disposed that when the main valve is in its central position the ports 25 25 both register with the ports 12 12, making a connection from the end of the cylinder 1 on one side of the piston 2 around through the main valve to the end of the cylinder on the other side of the piston 2. The connections from the peripheries of the piston-heads of the main valve to the central bore are formed by supporting projections 26 26, which prevent the separable end pieces 27 27 from closing down upon the ends of the central portion of the valve, thus leaving narrow circumferential passages or ports at 25 25, which connect with the hollow core of the valve through the spaces between the supporting projections 26 26.

The equalizing-passage is entirely distinct from the suction of the discharge passages or ports in the piston-valve, and therefore the pressure upon equalization is not effected by the pressure of the air contained in such passages.

In Fig. 1 the piston has reached the end of its stroke and has moved a very short distance to the right on the return stroke. The main valve moving to the right has reached its middle position, and the ports 25 25 are in full register with 12 12. All other connections from 7 7 and 8 have been closed ever since the ports 25 25 began to open, and the laps of valve 5 are such that they will remain closed until 25 is closed. Just as 25 opened the clearance-space on the left of the piston 2 was filled with air at discharge-pressure and the cylinder and clearance on the right of piston 2 were filled with air at suction-pressure. During the short interval in which the passage 4 14 12 25 5 25 12 14 4 is completed the small volume of air at high pressure on the left of piston 2 unites with the relatively large volume of air at low pressure to the right of piston 2, producing a mean pressure but slightly greater than that of suction, so that the piston 2 begins to do useful work on the suction side much earlier in the stroke than it otherwise would and the volumetric capacity of the machine is greatly increased. As piston 2 advances to the right connection is made on the left through passage 4, 14, 12. 7, and 6 to suction. At the same time connection at the right is made through 4 14 12 to 18. When the pressure to the right of piston 2 has reached or slightly exceeded that in chamber 8, the auxiliary valve 20' will move to the left, opening a connection through 19 to 8, thus allowing the air ahead of piston 2 to be discharged. When piston 2 shall have reached the end of its stroke to the right, valve 5, moving to the left, will have closed 12, cutting off the connection from the right of piston2to the discharge 8. Port 12 will remain closed to the discharge during the whole of the following stroke of the piston and the brief equalizing period on the succeeding stroke. During this interval, while port 12 is closed, the auxiliary valve 20 has been closed by the spring 21, not suddenly and noisily but slowly and quietly on account of the cushioningchamber 23. This slow closing movement of the auxiliary valve or puppet 20 is permissible on account of the long period available for its closing, which is equal to the period during which the discharge-port18 is entirely out of register with port 12. This period is equal to a full stroke of the pump-piston to the left plus the equalizing period. The equalizing period may be as much as five per cent. of the piston-stroke, so that the period available for the closing of the puppet 20 may be as much as one hundred and five per cent. of the piston-stroke. The actual time covered by this one hundred and five per cent. depends upon the speed at which the pump is driven. When the pump is being run slowly, the closing of the puppet 20 takes but a small fraction of this one hundred and five per cent. hen the pump is run very rapidly, the one hundred and five per cent. would represent such a short lapse of actual time that the closing of the puppet might occupy the whole of it. A speed such that the one hundred and five per cent. would be so short a time as to be entirely occupied by the closing of the puppet would be the maximum speed for efficient operation of the pump. As shown in Fig. 3, the eccentric center 5 is so located relatively to the crank center 3 that the main valve reaches its central position just after the beginning of a piston-stroke and starts to open the discharge-port of the cylinder after the piston has moved about five per cent. of its stroke. The equalizing takes place when the main valve is in its central position and justbefore the cylinder-ports are opened, during which time the air ahead of the piston is but little compressed, while the air behind the piston is at substantially maximum pressure. The one hundred and five per cent. is thus the period occupied by the piston in making a full stroke in one direction and the first five per cent. of its next stroke in the opposite direction. The same operations are effected by similar parts at each end of thc cylinder, suction alternating with discharge and equalizing occurring for a brief period at the beginning of each stroke.

In Figs. 4 and 5 is illustrated a modification in which puppet-valves 20 20 are used in place of the slide-valves 20 and 20 of Fig. 1. These valves are circular and are provided with circular seats 30 30. Discharge takes place through 14, 12, 18, and 31 and between the valve-seat 30 and the valve 20 when the valve 20 is off its seat. The operation of the valves 20 and 20 is similar to that of 20 20 of Fig. 1. Cushioning occurs just the same with this modification as in the form shown in Fig. 1, and the spring 15 acts in the same way to hold the valves upon their seats.

In the left-hand side of Fig. 5 the valveseat of Fig. 4 is shown in section on the line E F. The bridges 32 between the ports 31 are supported by posts 33 33, so as to stiffen the valve-seat against any deforming action of the valve 20.

In the modification shown in Figs. 6, 7, and 8 is shown a means which can, if desired, be used independently of the spring 21 for securing the return of the auxiliary valves 20 20 to their seats by a yielding pressure. This means consists in a connection 35 between the cushioning-chamber 23 and the hollow bore of the main valve, the connection 35 taking the place'of the ports 24, heretofore referred to. This passage is provided with a controllingscrew plug 36, by which its size may be varied. It will be noticed that the port 35 connects the cushioning-chamber with a hollow bore of the main valve. The pressure in this hollow bore is always equalizing pressure or less and always much lower than the discharge-pressure of the chamber 8. The action is as follows: The main valve moving to the left connects 12 and 18. When the pressure in 18 is slightly greater than that in 8, the valve 20 is moved toward the right, opening the passage 18 19 8. At the same time the valve 20 uncovers the port 35, which then connects the cushioning-chamber 23 with the hollow bore 5 of the main valve, constituting part of the equalizing-passage, in which air is at lower pressure than in the chamber 8. When the main valve again closes the port 12, the pressures in 18 and 8 become equal, and the pressure in 8 acting on the small unbalanced area on the right of the valve 20, due to the connection of the cushioning-chamber 23 with the equalizing-passage, will move valve 20 to the left, closing the port 19. Just before reaching its extreme position the valve 20 will close port 35, and the air entrapped in the cushioning-chamber 23 will be compressed as the valve 20 moves farther toward the left and will bring the valve 20 to rest quietly. The other auxiliary valve is a duplicate of the one illustrated and operates in the same manner.

In pumps of the character such as I have above described an appreciable amount of time is required for the auxiliary valves to seat, and the compressor should not be run at a speed greater than that which allows the valve to seat just before equalizing is completed. By controlling the discharge from each end of the cylinder independently by a separate auxiliary valve operated by yielding pressure the period in which these valves may close is about one hundred and five per cent. of the period occupied by a stroke of the piston, which gives ample time for the auxiliary valve to seat and removes the objection to the former design of speed limitation. In pumps as heretofore constructed, in which springpressure auxiliary valves common to both discharge-ports of the slide-valvehave been used, the period in which the valves could close was only about five per cent. of the piston-stroke, resulting in requiring the pumps to be run at a low speed. i

For compactness and convenience of construction I have reversed the usual practice in respect of suction and discharge passages; but I do not, therefore, wish to limit my broad invention to this construction or arrangement.

I have shown a piston main slide-valve, and I prefer this construction, as it is perfectly balanced at all times; but such a construction is not necessary to the embodying of my invention, since various other forms of valves could be substituted.

While I have described a valve system applicable to an air-compressor, I do not wish to be understood as limiting my construction to the handling of air alone, since this construction is applicable for other pumps handling other liquids or gaseous fluids where the pressure is above or below an atmospheric pressure-that is, to vacuum-pumps as well as to pressure-pumps.

WVhat I claim is* 1. In an air-pump the combination of a pump-cylinder, a valve-chamber connected therewith by ports at each end of said cylinder, a main valve in said chamber having corresponding ports disconnected from one another and having an equalizing passage formed entirely within the body of the valve and independent of the suction and discharge passages-and adapted to connect the two ends of said cylinder, separate auxiliary valves for independently controlling said main valveports, said auxiliary valves being carried by said main valve, a discharge-passage leading from the discharge sides of said auxiliary valves and .a suction-passage leading to the suction side of said main valve.

2. In an air-pump, the combination of a pump-cylinder, a valve-chamber having suc- IIS tion and discharge openings and connected to said pump-cylinder by ports at each end of said cylinder, a balanced main valve in said chamber dividing it into a suction-chamber and a discharge-chamber, and having a passage corresponding to the ports at one end of said cylinder and adapted to register therewith, and also a passage corresponding to the ports at the other end of said cylinder and adapted to register therewith, said passages being disconnected from one another and leading to said discharge-chamber, separate auxiliary discharge-valves carried by said balanced main valve and seated thereon, one of said auxiliary discharge-valves being located between one of said passages and the discharge-chamber, and the other of said auxiliary valves being located between the other of said passages and the discharge-chamber, said auxiliary valves opening in such direction that the pressure of air delivered past one of said auxiliary valves cooperates with reservoir-pressure to hold the other closed, so that each of the auxiliary valves controls the discharge through its passage independently of the other valve.

3. In an air-pump, the combination of a pump-cylinder, a valve-chamber connected thereto by ports at each end of said cylinder, a main piston-valve therein having piston-heads with corresponding ports, separate and independently-actuated auxiliary valves mounted on the inner sides of the piston-heads of said main piston-valve, means for holding said valves to their seats with a yielding pressure, a discharge-passage leading from the inside of said piston-heads and a suction-passage leading to the other sides of said piston-heads.

4:. In an air-pump, the combination of a pump-cylinder, a valve-chamber connected thereto by ports at each end of said cylinder, a main piston-valve therein having pistonheads with corresponding ports, separate auxiliary valves mounted on the inner sides of the piston-heads of said main piston-valve and surrounding the axis of the same, means for holding said valves to their seats with a yielding pressure, a discharge-passage leading from the inside of said piston-heads and a suction-passage leading to the other sides of said piston-heads.

5. In an air-pump, the combination of a pump, a cylinder, a valve-chamber connected thereto by ports at each end of said cylinder, a main piston-valve therein having pistonheads with corresponding ports, separate auxiliary cylindrical valves mounted on the inner sides of the piston-heads of said main pistonvalve, and surrounding the axis of the same, means for holding said valves to their seats with a yielding pressure, a suction-passage leading to the outside of said piston-heads and a discharge-passage leading from the other sides of said piston-heads.

6. In an air-pump, the combination of a pump-cylinder, a valve-chamber connected thereto by ports at each end of said cylinder, a main piston-valve therein having pistonheads with corresponding ports, separate auxiliary valves mounted on the inner sides of the piston-heads of said main piston-valve, and surrounding the axis of the same, means for exerting upon said valves a spring-pressure, a suction-passage leading to the outside of said piston-heads and a discharge-passage leading from the other sides of said pistonheads.

7. In an air-pump, the combination of a pump-cylinder, a valve-chamber connected thereto by ports at each end of said cylinder, a main piston-valve therein having pistonheads with corresponding ports, separate auxiliary valves mounted on the inner sides of the piston-heads of said main piston-valve, and surrounding the axis of the same, a spring engaging with both of said valves to hold the same to their seats with a yielding pressure, a suction-passage leading to the outside of said piston-heads and a discharge-passage leading from the other sides of said pistonheads.

8. In an air-pump the combination of a piston, a pump-cylinder therefor, a valve-chamber connected to said cylinder and having suction and discharge passages, a piston-valve therein alternately connecting the two ends of said cylinder with said suction and discharge passages, said. piston-valve having an equalizing-passage lying entirely within the body of said valve and independent of the suction and discharge passages and thereby at intermediate times connecting both ends of said cylinder with each other.

9. In an air-pump having a pump-cylinder and valve-cham ber with suction and discharge passages, a piston-valve consisting of a rod, a hollow body having two piston-heads thereon, said piston-heads having passages connected with the hollow of said body and registering with ports at each end of the pumpcylinder at a time when said pump-cylinder is separated by said valve from both the suction and discharge passages.

10. In an air-pump, a piston-valve consisting of a rod, a divided body having two piston-heads thereon, auxiliary valves surrounding said body, means for holding said auxiliary valves to their seats and means for clamping the parts of said divided body upon said rod.

11. In an air-pump having a pump-cylinder and a valve-chamber with suction and discharge passages, a piston-valve consisting of a rod, a divided hollow body having two piston-heads thereon, provided with dischargeports, auxiliary valves surrounding said hollow body, means for holding said auxiliary valves to their seats and means for clamping the parts of said divided body upon said rod, saidpiston-heads having additional passages connected to the hollow bore of said body and registering with ports at each end of the pumpcylinder at a time when said cylinder is separated by said valve from both the suction and discharge passages.

Signed at New York, N. Y., this 12th day of May, 1904.

THEODORE N. CASE.

Witnesses:

H. B. BROWNELL; L. VREELAND. 

